Jan. 4 (Bloomberg) -- NASA's robot geologist Spirit landed safely on Mars after a seven-month, 300 million-mile (483 million -kilometer) journey to seek evidence that liquid water may have existed there, a possible sign the planet once supported life.

The space agency's Jet Propulsion Laboratory in Pasadena, California, received a signal from the surface at 8:51 p.m. Pacific time that the landing craft carrying the golf-cart-size rover had arrived after a violent, six-minute descent from 80 miles up. Mission plans called for airbags to envelop the craft above the desert planet, allowing the package to bounce like a beach ball before stopping.

``It is positive confirmation that the rover has landed safely,'' said Belle Philibosian, a spokeswoman with the Jet Propulsion Laboratory.

Spirit landed at a site called Gusev Crater, which is at the end of an ancient riverbed channel and may have been a crater lake. Opportunity, a sibling rover, is scheduled to land in three weeks on the other side of Mars at Meridiani Planum, which has a large deposit of gray hematite, a mineral that usually forms in a wet environment.

The two probes were sent to Mars, at a cost of $820 million, to take advantage of the proximity of the red planet to Earth. On Aug. 27, the planets had their closest encounter in 60,000 years, and Mars appeared as a bright, reddish orb even without binoculars. Mars came as close as 34.6 million miles, or about a quarter of its usual distance.

Earth was 105.7 million miles away when Spirit landed, according to JPL.

The rovers will venture as far as 1 kilometer, or about six- tenths of a mile, around the landing sites and will use a ``rock abrasion tool'' to bore for samples and spectrometers to detect minerals.

Robotic Geologist

For Earth-bound spectators, the most dramatic observations from Spirit and Opportunity may come from panoramic pictures they are to shoot from cameras mounted at human-eye height. Photographs taken during the 1997 Pathfinder landing mission were posted on Web sites and aired on television screens worldwide.

Unlike the pioneering, $1 billion Viking landers of 1976, the rovers won't carry out biochemistry experiments with Martian soil to detect the presence of microorganisms. The Viking experiments offered no conclusive evidence that life was present.

Spirit will spend nine days in a careful sequence of steps before it leaves its lander platform. The other robot rover, Opportunity, was launched July 7 and is following behind, scheduled to land on the other side of Mars on Jan. 25.

Spirit's lander, hauling the 400-pound (181-kilogram) robotic geologist to the surface, had to slow from 12,000 mph in six minutes to a stop, after entering the atmosphere.

Airbags

Friction in the atmosphere braked the craft to about 1,000 mph, and parachutes deployed at about the cruising altitude of a commercial jetliner on Earth. Before the airbags deployed, rockets fired about 300 feet up to reduce the craft's velocity.

NASA space science chief Edward Weiler called the entry ``six minutes of hell.''

NASA plans to follow the rovers with an orbiter in 2005 that can map features as small as a basketball, an advanced rover in 2009 that can range across tens of kilometers for as long as a year, and a satellite the same year that will pioneer an optical communications system to speed information to Earth.

While a rover was successfully landed on the planet for the first time in 1997, the two new missions will operate with more capable machines. The 1997 rover, called the Sojourner, drove no further than 100 meters around its landing area.

Two of every three attempts by the U.S. and other nations to complete a Mars landing have failed. NASA lost a landing craft and orbiting spacecraft in 1999 because of technical mistakes, wiping out projects worth almost $300 million and forcing a management shakeup in the Mars exploration effort.

Europe's first voyager to Mars, the British-built Beagle 2, has failed to make contact since its scheduled touchdown on the planet Dec. 25, and may be in a crater found near the landing site. The craft was supposed to dig beneath the Martian surface and transmit data back to Earth using NASA technology.

Last Updated: January 4, 2004 00:30 EST